Method of manufacturing a striking face of a golf club head

ABSTRACT

An improved striking face of a golf club head and a method of manufacturing thereof is disclosed herein. More specifically, the present invention discloses an improved method of stamped forging variable face geometry onto the rear surface of a striking face from a frontal portion of the striking face; wherein the improved process allows for more precise finished parts with less need for complicated machining. The resulting striking face of a golf club head comprises of a substantially planar frontal surface and a substantially non-planar rear surface, wherein the substantially non-planar rear surface is created via a stamped forging process while the substantially planar frontal surface is created via a machining process.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 13/467,102, to Myrhum et al., Striking Face of a Golf Club Head anda Method of Manufacturing the same, filed on Jun. May 9, 2012, currentlypending, the disclosure of which is hereby incorporated by reference inits entirety.

FIELD OF THE INVENTION

The present invention relates to a striking face of a golf club head anda method of manufacturing the same. More specifically, the presentinvention relates to an improved method of stamped forging variable facegeometry onto the rear surface of a striking face from a frontal portionof the striking face; wherein the improved process allows for moreprecise finished parts with less need for complicated machining. Theresulting striking face of a golf club head comprises of a substantiallyplanar frontal surface and a substantially non-planar rear surface,wherein the substantially non-planar rear surface is created via astamped forging process while the substantially planar frontal surfaceis created via a machining process.

BACKGROUND OF THE INVENTION

Ever since the metalwood golf club burst onto the scene to replace thetraditional persimmon wood, golf club designers have constantly soughtto find ways to improve upon this groundbreaking design.

U.S. Pat. No. 5,474,296 to Schmidt et al. illustrate one of the earlierattempts to improve upon the design opportunity created by a hollowmetalwood golf club by disclosing a golf club with a variable faceplatethickness. One way a variable faceplate thickness improves theperformance of a metalwood club is by reducing the amount of weight atlow stress areas of the striking faceplate to create more discretionaryweight that can be placed at alternative locations in the golf club headto improve the performance of the golf club head. In addition to theabove benefit, the incorporation of variable faceplate thickness canalso improve upon the performance of the golf club head by adjusting thecoefficient of restitution of the striking face.

U.S. Pat. No. 6,863,626 to Evans et al. illustrates this secondarybenefit of adjusting the coefficient of restitution of a golf club bydisclosing a golf club having a striking plate with regions of varyingthickness. More specifically, U.S. Pat. No. 6,863,626 identifies thisbenefit by indicating that striking plate having regions of varyingthickness allows for more compliance during impact with a golf ball,which in turn, could generate more ballspeed.

U.S. Pat. No. 7,137,907 to Gibbs et al. illustrates the ability tofurther improve upon the design of a striking face having a variableface thickness for a purpose that is different from saving weight andimproving coefficient of restitution. More specifically, U.S. Pat. No.7,137,907 illustrates a way to expand upon the “sweet spot” of a golfclub head in order to conform to the rules of golf that puts a cap onthe maximum coefficient of restitution allowed by a golf club. U.S. Pat.No. 7,137,907 does this by disclosing a golf club face or face insertwherein the face has an interior surface with a first thickness sectionand a second thickness region. The first thickness section preferablyhas a thickness that is at least 0.025 inch greater than the thicknessof the second thickness region. The face or face insert with variablethickness allows for a face or face insert with less mass in a golf clubhead that conforms to the United States Golf Association regulations.

With the incorporation of variable face thickness into hollow metalwoodtype golf club heads, various methodologies of manufacturing have beendeveloped to create this complicated geometry. U.S. Pat. No. 6,354,962to Galloway et al. illustrates one methodology to create a strikingwherein the face member is composed of a single piece of metal, and ispreferably composed of a forged metal material, more preferably a forgedtitanium material. However, due to the need for precise geometry, thevariable face geometry created by this conventional forging process mayoften exhibit waviness which will often need to be machined to the exactprecise geometry. U.S. Pat. No. 7,338,388 to Schweigert et al. discussesthis machining process by utilizing a ball end mill revolving about anaxis generally normal to the inner surface of the face plate at aninitial location on a circumferential intersection between the outeredge of the central thickened region and a transition region. The innersurface of the face plate is machined by moving the revolving ball endmill in a radial direction outwardly toward and through the transitionregion and the peripheral region to machine the inner surface of theface plate creating a tool channel having a width as the ball end milltraverses the transition region and thereby vary the thickness of theface plate in the tool path.

Although the machining process described above may be capable ofcreating a very precise geometry, the resulting striking face couldstill be flawed due to some inherent machining side effects. Undesirableside effects such as the existence of machine marks, circular cuttingpatterns, discontinuity of machine lines, starting and stopping marks,and/or machine chatters could all adversely affect the striking face.

U.S. Pat. No. 6,966,848 to Kusumoto attempts to address this issue oftrying to create an improved striking face of a golf club head bydisclosing a methodology wherein the stamped out face material is placedin a die assembly, wherein the face material is being thinned by causingthe face material to plastically deform via pressing an upper dietogether with the lower die. Although this particular type ofconventional forging methodology eliminates the adverse side effects ofmachining above described, it suffers from an entirely different set ofadverse side effect. More specifically, the conventional forging of aface insert suffers from lack of material consistency and materialtransformation that results when a material is melted and plasticallydeformed resulting in grain growth and oxidation; both of which canlower the material strength of a material.

In addition to the above flaws in the current manufacturing techniques,these flaws of the current techniques become even more apparent when adesigner seeks to further advance the performance of a striking face byimplementing non-symmetrical geometries that would either requireextensive machining, or extreme sacrifice in material property dependingon the solution selected.

Hence, as it can be seen from above, despite all the attempts inaddressing the consistency and accuracy issue in creating the variableface geometry in a golf club head striking face, the current art fallsshort in providing a methodology that can address the issues above.Ultimately, it can be seen from above that there is a need in the artfor a methodology of creating the striking face portion of a golf clubhead with variable face geometry without relying on materialconventional property changing forging techniques or simple machiningtechniques to ensure more precision and consistency for basicsymmetrical geometries and even extreme asymmetrical geometries.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a striking face of a golf clubhead comprising of a substantially planar frontal surface, and asubstantially non-planar rear surface, wherein the substantially planarfrontal surface and the substantially non-planar rear surface combine tocreate a central region having a first thickness encompassing ageometric center of said striking face, a transition regioncircumferentially encompassing said central region, and a perimeterregion circumferentially encompassing said transition region. Thesubstantially non-planar rear surface is created via a stamped forgingprocess and the substantially planar frontal surface is created via amachining process.

Another aspect of the present invention is a method of forming astriking face of a golf club head comprising of placing a pre-form faceinsert between a top punch and a bottom cavity; the top punch having aprotrusion and the bottom cavity having a depression, compressing thetop punch against the bottom cavity to alter a shape of the pre-formface insert to create a substantially non-planar rear surface, andmachining off excess material from a top punch side of the pre-form faceinsert to create a substantially planar frontal surface. Thesubstantially non-planar rear surface of the pre-from face insert has anon-symmetrical shape about its vertical dividing line, the verticaldividing line defined as a line drawn vertically through the crown andsole portion of the face insert passing through a face center.

A further aspect of the present invention is a method of forming astriking face of a golf club head comprising of placing a pre-form faceinsert between a top punch and a bottom cavity; the top punch having aprotrusion and the bottom cavity having a depression, compressing thetop punch against the bottom cavity to alter a shape of the pre-formface insert to create a substantially non-planar rear surface, andfilling the rear indentation of the pre-form face insert that is createdby the protrusion of the top punch with a secondary material, whereinthe secondary material is a different material than a material used forthe pre-form face insert.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of the invention as illustratedin the accompanying drawings. The accompanying drawings, which areincorporated herein and form a part of the specification, further serveto explain the principles of the invention and to enable a personskilled in the pertinent art to make and use the invention.

FIG. 1 shows a perspective view of a golf club head that is disassembledin accordance with an exemplary embodiment of the present invention;

FIG. 2 shows an internal rear view of a face insert in accordance withan exemplary embodiment of the present invention;

FIG. 3 shows a cross-sectional view of a face insert in accordance withan exemplary embodiment of the present invention;

FIG. 4a shows a side view of one of the steps used to create a faceinsert in accordance with an exemplary embodiment of the presentinvention;

FIG. 4b shows a side view of one of the steps used to create a faceinsert in accordance with an exemplary embodiment of the presentinvention;

FIG. 4c shows a side view of one of the steps used to create a faceinsert in accordance with an exemplary embodiment of the presentinvention;

FIG. 5a shows a side view of one of the steps used to create a faceinsert in accordance with an exemplary embodiment of the presentinvention;

FIG. 5b shows a side view of one of the steps used to create a faceinsert in accordance with an exemplary embodiment of the presentinvention;

FIG. 5c shows a side view of one of the steps used to create a faceinsert in accordance with an exemplary embodiment of the presentinvention;

FIG. 6a shows a cross-sectional view of a face insert in accordance withan alternative embodiment of the present invention; and

FIG. 6b shows a cross-sectional view of a face insert in accordance witha further alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description describes the best currentlycontemplated modes of carrying out the invention. The description is notto be taken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the invention, since the scope ofthe invention is best defined by the appended claims.

Various inventive features are described below and each can be usedindependently of one another or in combination with other features.However, any single inventive feature may not address any or all of theproblems discussed above or may only address one of the problemsdiscussed above. Further, one or more of the problems discussed abovemay not be fully addressed by any of the features described below.

FIG. 1 of the accompanying drawings shows a perspective view of a golfclub head 100 wherein a body portion 102 and a face insert 104 aredisassembled to show the variable face thickness at a rear portion ofthe face insert 104. It should be noted in FIG. 1 the golf club head hasthe face insert 104 forming the striking face portion of the golf clubhead 100 as one of the exemplary embodiments. However, a face insert 104type geometry is not the only way to form the striking face portion, infact numerous other geometries can be used to form the striking faceportion such as a C shaped face cup, a L shaped face cup, a T shapedface cup, or any other suitable geometry all without departing from thescope and content of the present invention.

FIG. 2 of the accompanying drawings shows a more detailed enlargedperspective view of a face insert 204 in accordance with an exemplaryembodiment of the present invention. More specifically, the internalback view of the face insert 204 allows the face center 210, centralregion 212, transition region 214, and the perimeter region 216 to allbe easily shown. In addition to showing the various regions, FIG. 2 ofthe accompanying drawings shows a cross-sectional line A-A′ horizontallydividing the face insert 204 to illustrate the relative thicknesses ofthe various regions in FIG. 3. This cross-sectional line A-A′ may alsobe known as the horizontal dividing line, spanning horizontally throughthe heel and toe portion of said face insert passing through a facecenter 210. FIG. 2 also shows a vertical dividing line B-B′, that spansvertically through the crown and sole portion of said face insertpassing through a face center 210.

FIG. 3 of the accompanying drawings shows a cross-sectional view of theface insert 304 taken across cross-sectional line A-A′ as shown in FIG.2. It should be noted that FIG. 3 of the present invention shows acentral region 312 having a first thickness d1, a first transitionregion 314 having a second thickness d2, a first perimeter region 316having a third thickness d3, a second transition region 313 having afourth thickness d4, and a second perimeter region 315 having a fifththickness d5. In one exemplary embodiment, wherein the geometry of thevariable face thickness is symmetrical, the thickness of the first andsecond transition regions 313 and 314 are the same and the thickness ofthe first and second perimeter region 315 and 316 are the same. Itshould be noted that due to the fact that the transition regions 313 and314 are constantly transitioning in thickness from the central region312 to the perimeter regions 315 and 316, the thickness of thetransition regions 313 and 314 are measured at the center of thetransition regions 313 and 314. In some instances it is preferred tohave symmetry in the variable face thickness geometry, as it makes forfairly simple and straight forward machining. However, the symmetricalgeometry may not truly optimize the weight and performancecharacteristics of a striking face, and has generally stemmed from themachining problems that can come with asymmetrical geometries.

Hence, in accordance with an alternative and preferred embodiment of thepresent invention, the face insert 304 may have an asymmetricalgeometry. More specifically, the first transition region 314 may have asecond thickness d2 that is different from the fourth thickness d4 ofthe second transition region 313, and the first perimeter region 316 mayhave a third thickness d3 that is different from the fifth thickness d5of the second perimeter region 315. Removing the restriction ofsymmetrical variable face thickness geometry removes unnecessary designrestrictions to allow a golf club designer to truly optimize the facedesign. In fact, the preference for symmetrical face geometries in aface insert has always been driven by manufacturing preferences. In oneexemplary embodiment, a golf club designer could further thin outdifferent regions of the striking face that is not subjected to thehighest level of stress, creating more discretionary mass to be moved todifferent regions of the golf club head itself.

In this exemplary embodiment, thickness dl of the central region 312 maygenerally be greater than about 3.0 mm, more preferably greater thanabout 3.30 mm, and most preferably greater than about 3.60 mm. Thicknessd2 and d4 of the transition regions 314 and 313 respectively maygenerally decrease from about 3.60 mm to about 2.7 mm, more preferablyfrom about 3.60 mm to about 2.65 mm, and most preferably from about 3.60mm to about 2.60 mm. Finally, thickness d3 and d5 of perimeter regions316 and 315 respectively may generally also be decreasing from about2.70 mm to about 2.55 mm, more preferably from about 2.65 mm to about2.50 mm, and most preferably from about 2.60 mm to about 2.45 mm.

Based on the above, it can be seen that a new methodology needs to becreated to effectively create this constantly changing face thicknesswithout the need to machine complicated geometry that is asymmetrical.The current invention, in order to achieve this goal has created aninnovative machining process detailed in FIGS. 4a, 4b, 4c, 5a, 5b, and5c shown in the later figures.

FIG. 4a through FIG. 4c illustrates graphical depiction of the newinnovative face insert forming technique associated with an exemplaryembodiment of the present invention called “stamped forging”. Althoughthis new innovative forming technique may have some similarities to theconventional forging process, it is completely different. In fact, theconventional forging process involves deformation of the face insert 404pre-form material to create the material flow into a cavity. Thismelting of the material is undesirable when used to form the strikingface portion of the golf club head, as the melting of the material,combined with the phase transformation of the material, could result ingrain growth and oxidation of the titanium material, both of whichdiminishes the material strength of titanium.

The current process is completely different from the conventionalforging process because it involves the elements of stamping as well asforging, and can be more accurately described as “stamped forging” or“embossed forging”. During this “stamped forging” or “embossed forging”process the face-insert 404 pre-form does not experience any phasetransformation, but is merely warmed to a malleable temperature to allowdeformation without the actual melting of the face insert 404 pre-form.

More specifically, in FIG. 4a , a side view of the first step in thecurrent forming technique is shown. In FIG. 4a , the various componentsused for the formation of the face insert 404 such as the top punch 421and bottom cavity 422 are shown in more detail. More specifically, as itcan be seen from FIG. 4a , the top punch 421 has a protrusion 424created in roughly the shape of the desired variable face thicknessgeometry; while the bottom cavity 422 has a corresponding depression 426that also roughly corresponds to the shape of the desired variable facethickness geometry. Although not shown in extreme detail, FIG. 4a showsthat the bottom cavity 422 could be non-linear along the perimeter edges427 to create a constantly variable thickness across the entireperimeter surface of the face insert 404 pre-form.

FIG. 4b shows the next step of the current inventive stamped forgingmethodology wherein the top punch 421 compresses against the bottomcavity 422 to alter the shape and geometry of the face insert 404.Although the current inventive methodology does not involve the meltingof the material used to create the face insert 404, the face insert 404is generally heated up to about 830° C. for about 300 seconds on aconveyor belt to increase the malleability of the face insert 404 toallow for the deformation. In this current exemplary embodiment of theinvention the top punch 421 generally applies about 100 MPa of pressureonto the face insert 404 for about 2 seconds to create the desiredgeometry.

FIG. 4c shows the next step of the current inventive stamped forgingmethodology wherein the shape of the variable face thickness geometrybegins to take place when the top punch 421 is removed from the bottomcavity 422. It should be noted here that in this current exemplaryembodiment of the present invention, the side of the face insert 404that faces the top punch 421 will eventually form the external surfaceof the face insert 404 as it gets assembled in the golf club head, whilethe side of the face insert 404 that contacts the bottom cavity 422 willeventually form the internal surface of the face insert 404 as it getsassembled in the golf club head. This type of methodology ensures that aprecise geometry could be achieved on the internal side of the faceinsert 404 without the need for excessive machining, even if anon-symmetrical organic shape is desired to maximize the performance ofthe face insert 404.

Although the steps described above in FIGS. 4a through 4c may besufficient to create the desired geometry in some circumstances,additional steps similar to the ones described above may be repeated toachieve more precise and complicated geometries. In the alternativeembodiments wherein multiple stamped forging steps are required, theprocess could be repeated for rough and fine stamped forging withoutdeparting from the scope and content of the present invention. In fact,the steps described could be repeated three time, four times, or anynumber of times necessary to achieve the desired geometry all withoutdeparting from the scope and content of the present invention. In caseswherein multiple stamped forging steps are needed, the shape andgeometry of the top punch 421 and the bottom cavity 422 may even beslightly different from one another, with each finer mold having acloser resemblance to the final finished geometry.

Once the geometry of the internal surface of the face insert 404 isformed via the above prescribed methodology, the external surface of theface insert 404 can be machined off a flat geometry, which is asignificant improvement than the conventional methodology of actuallymachining in the complicated geometry on the rear internal surface ofthe face insert 404. FIGS. 5a through 5c illustrate the final stepsinvolved in machining off the excess material in this the current faceinsert 504 stamped forging methodology.

FIGS. 5a-5c show side views of a face insert 504 together with thebottom cavity 522 after the top punch (not shown) has created thedesired geometry by deforming the shape of the face insert 504 in theprevious steps. In these final steps, the excess material of the faceinsert 504 is removed via a cutter 530. The excess material, as shown inthis current exemplary embodiment of the present invention, maygenerally be defined as any material that is above the cutting line 531shown in FIG. 5a . This cutting line 531 is generally defined by theflat surface that significantly aligns with the bottom of the rearindentation 528 of the formed face insert 504. In fact, in mostexemplary embodiments, the cutting line 531 may actually be placedslightly below the bottom of the rear indentation 528 of the formed faceinsert 504 to allow for a precise finish of the face insert 504.

The position of this cutting line 531 can be important, as it determinesthe relative thickness of the face insert 504. Hence, in order to moreaccurately define this cutting line 531, distance d6 and d7 areidentified in FIG. 5a . Here, in this current exemplary embodimentdistance d6 signifies the distance of the final thickness of theperimeter relative to the perimeter surface of the bottom cavity 522.This distance d6 may generally vary from about 2.2 mm to about 2.6 mm,more preferably from about 2.3 mm to about 2.6 mm, and most preferablyfrom about 2.4 mm to about 2.6 mm. However, as it has already beendiscussed before the perimeter region of the face insert 504 could verywell have a variable thickness, thus making it difficult to determinethe thickness of d6; as the thickness d6 would be a function of theperimeter of the face insert 504. Thus, in order to properly index thecutter 530 to remove the correct amount of material from the frontalsurface of the striking face 504, an additional thickness d7 isidentified; measuring the distance from the bottom of the depression 526of the bottom cavity 522 to the cutting line 531 from which the removalof material is indexed. Distance d7, as it is shown in this currentexemplary embodiment of the present invention, may generally be betweenabout 3.5 mm to about 3.8 mm, more preferably between about 3.6 mm toabout 3.7 mm, and most preferably about 3.65 mm.

The cutter 530 shown in this current exemplary embodiment of the presentinvention may generally be a fly cutter type cutter to ensure a smoothsurface that will eventually form the frontal surface of a golf clubhead, however, numerous other types of cutters may be used withoutdeparting from the scope and content of the present invention. Morespecifically, alternative cutters 530 may include an end mill clutter, aball nose cutter, a side and face cutter, a woodruff cutter, a shellmill cutter, or any type of milling cutter all without departing fromthe scope and content of the present invention. In fact, the finishedsurface could even potentially be achieved by any alternative finishingtechniques that could create a flat surface all without departing fromthe scope and content of the present invention.

FIG. 5b shows an intermediary stage of the cutting process wherein thecutter 530 begins to remove excess material from the formed face insert504 along cutting line 531. Finally, FIG. 5c shows the finished productof a face insert 504 in accordance with an exemplary embodiment of thepresent invention wherein the excess material has been removed by thecutter 530. The finished face insert 504 can then be bent to therequired curvature to match the bulge and roll of a golf club head andinstalled to complete the golf club head. As it can be seen from above,the innovative forming and finishing method is a major improvement insimplifying the machining process involved to a simple one pass finish,especially when compared to the conventional method of machining theactual variable thickness geometry. This advantage of not having tomachine the actual geometry becomes even more apparent when the variablegeometry implemented involves non-symmetrical shapes, as those types ofgeometries become extremely difficult to machine using conventionalmachining methods.

FIGS. 6a and 6b show alternative embodiments of the present inventionwherein the frontal indentation 628 of the striking face insert 622 arepreserved and not machined off. In these embodiments, the frontalindentation 628 could be filled with a secondary material that isdifferent from the material used to create the face insert 622 to createa striking face insert 622 that incorporates multiple materials. Thefiller 630 in this current exemplary embodiment could be made out ofsteel, aluminum, tungsten, composites, or any other types of materialthat can be reasonably adhered to the rear indentation 628 of the faceinsert 622 without departing from the scope and content of the presentinvention. The filler 630 material may have a have a second densitygreater than a density of the material used to create the face insert622 in one exemplary embodiment of the present invention; however, in analternative embodiment of the present invention, the filler 630 materialmay also have a second density that is less than the density of thematerial used to create the face insert 622 without departing from thescope and content of the present invention. In an alternativeembodiment, the frontal indentation 628 could be filled with a filler630 that is made out of a similar type material as the remainder of theface insert 622 to ensure sufficient bonding and cohesion between thematerials. More specifically, in this alternative embodiment, the filler630 material could be Ti-64, Ti-811, SP-700, ATI-425, or any other typeof titanium alloys all without departing from the scope and content ofthe present invention.

FIG. 6b shows a further alternative embodiment of the present inventionwherein the external surface of the face insert 622 could be coveredwith a cover layer 632 to ensure that the entire external surface of theface insert 622 has the same material to conform with the requirementsof the USGA. In one exemplary embodiment of the present invention thecover layer 632 may be made out of titanium type material similar to theremainder of the body; however, different types of titanium alloys couldbe used without departing from the scope and content of the presentinvention as long as it is capable of covering the external surface ofthe face insert 622.

Other than in the operating example, or unless otherwise expresslyspecified, all of the numerical ranges, amounts, values and percentagessuch as those for amounts of materials, moment of inertias, center ofgravity locations, loft, draft angles, various performance ratios, andothers in the aforementioned portions of the specification may be readas if prefaced by the word “about” even though the term “about” may notexpressly appear in the value, amount, or range. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in theabove specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

It should be understood, of course, that the foregoing relates toexemplary embodiments of the present invention and that modificationsmay be made without departing from the spirit and scope of the inventionas set forth in the following claims.

What is claimed is:
 1. A method of forming a striking face of a golfclub head comprising: placing a pre-form face insert between a top punchand a bottom cavity; said top punch having a protrusion and said bottomcavity having a depression, compressing said top punch against saidbottom cavity to alter a shape of said pre-form face insert to create asubstantially non-planar rear surface; and machining off excess materialfrom a top punch side of said pre-form face insert to create asubstantially planar frontal surface; wherein said substantiallynon-planar rear surface of said pre-form face insert has anon-symmetrical shape about its vertical dividing line, said verticaldividing line defined as a line drawn vertically through the crown andsole portion of said face insert passing through a face center.
 2. Themethod of forming the striking face of a golf club head of claim 1,further comprising: heating said pre-form face insert to a temperatureof about 830° C. before placing said pre-form face insert between saidtop punch and said bottom cavity.
 3. The method of forming the strikingface of a golf club head of claim 2, wherein said step of heating saidpre-form insert to about 830° C. lasts for about 300 seconds.
 4. Themethod of forming a striking face of a golf club head of claim 1,wherein said step of compressing said top punch against said bottomcavity applies about 100 MPa of pressure onto said pre-form face insert.5. The method of forming a striking face of a golf club head of claim 1,wherein the step of machining off the excess material further comprises:indexing a distance from a bottom surface of said depression of saidbottom cavity, machining off any excess material that is thicker thansaid distance from said bottom surface of said depression of said bottomcavity; wherein said distance is between about 3.5 mm to about 3.8 mm.6. The method of forming a striking face of a golf club head of claim 5,wherein said distance is between about 3.6 mm to about 3.7 mm.
 7. Themethod of forming a striking face of a golf club head of claim 6,wherein said distance is about 3.65 mm.